The invention relates to new and useful improvements in aircraft navigation and airspace control systems, and more particularly to such systems using the global positioning system and the microwave landing system.
In recent years aircraft navigation and airspace control have been vastly improved by introduction of the global positioning system (GPS) and the microwave landing system (MLS). These systems supplement the existing inertial navigation systems (INS) or radionavigation systems currently used for enroute navigation, and instrument landing system (ILS) for terminal guidance. GPS uses special radio receivers in an aircraft to receive radio signals transmitted from an array of earth satellites. Using the information from the satellites, an aircraft receives and calculates its position within 50-150 feet in all three dimensions. The MLS replaces the VHF ILS with an approach and landing system using microwave signals. This provides a much more accurate and flexible landing system which permits the number of takeoff and landing operations at an airport to be sharply increased.
In the present practice, the GPS, INS and MLS systems are used separately at the discretion of the pilot, or the GPS and INS data are combined to give integrated GPS/INS enroute navigation information. The transition from GPS/IN navigation used enroute to the MLS navigation needed for landing is manual and is determined by the pilot. This transition from one navigation system to another normally occurs at a time of high cockpit workload and navigational uncertainty and thus can decrease aircraft safety. In addition, the transition is abrupt and the flight path can be adversely affected by the differences due to errors in each device. Due to such discrete transitions, extra reliance must be placed upon ground controller vectoring, especially when combined with a specified time of arrival for spacing and sequencing. Since ground controllers are otherwise fully occupied, the extra work related to ground vectoring increases the chances of mistakes by controllers which can compromise safety. Further, each of these devices is subject to errors, and independent operation does not use one device to check the accuracy of the others.
It is therefore an object of the present invention to provide an aircraft navigation system which integrates the GPS/INS and MLS navigation systems.
It is another object of the present invention to provide an aircraft navigation system which gradually shifts between the GPS and MLS systems.
It is a further object of the present invention to provide an aircraft navigation system which minimizes errors associated with switching from the GPS/INS navigation system to the MLS navigation system.
It is an additional object of the present invention to provide a highly automated enroute, transition and terminal navigation system.
It is yet another object of the present invention to provide an aircraft navigation system which uses the optimimum type of navigation information for each phase of an aircraft mission or flight.
It is yet a further object of the present invention to provide crosschecking of several navigation systems to detect anomalous errors and to automatically compensate therefor.
It is yet an additional object of the present invention to provide a multi-source aircraft navigation system which decreases cockpit workload in critical phases of a flight and thus decreases the chances of mishap resulting from crew distraction or navigational uncertainty.
It is still another object of the present invention to provide an aircraft navigation system which minimizes the need for ground controller vectoring.
It is still an additional object of the present invention to provide an integrated navigation system which relies soley upon MLS guidance for final terminal guidance in accordance with certification criteria for landing approaches.
Still other objects will become apparent in the following summary and description of a preferred embodiment of the invention.